Functionalized polymers for medical applications

ABSTRACT

The present invention is directed to synthetic, biodegradable, biocompatible polymers that are the reaction product of an α,β-unsaturated polybasic acid or derivative thereof and a monoglyceride, and which further contain pended thereto a functional agent, and to medical devices and compositions containing such polymers.

FIELD OF THE INVENTION

The present invention relates to synthetic, biodegradable, biocompatiblepolymers for use in pharmaceutical and medical applications and tocompositions and medical devices containing such polymers.

BACKGROUND OF THE INVENTION

Both natural and synthetic polymers, including homopolymers andcopolymers, which are both biocompatible and biodegradable in vivo areknown for use in the manufacture of medical devices that are implantedin body tissue and that are absorbed or passed by the body over time.Examples of such medical devices include suture anchor devices, sutures,staples, surgical tacks, clips, plates, screws, drug-delivery devices,adhesion prevention films and foams, and tissue adhesives.

Natural polymers may include catgut, cellulose derivatives and collagen.Natural polymers typically are absorbed by the body after enzymaticdegradation of the polymers in the body.

Synthetic polymers may include aliphatic polyesters, polyanhydrides andpoly(orthoester)s. Such polymers typically degrade by a hydrolyticmechanism in the body and then are absorbed by the body. Such syntheticpolymers include homopolymers, such as poly(glycolide), poly(lactide),poly(e-caprolactone), poly(trimethylene carbonate) andpoly(p-dioxanone), and copolymers, such as poly(lactide-co-glycolide),poly(e-caprolactone-co-glycolide), poly(glycolide-co-trimethylenecarbonate), poly(alkylene diglycolate), and polyoxaesters. The polymersmay be statistically random copolymers, segmented copolymers, blockcopolymers or graft copolymers.

Alkyd-type polyesters prepared by the polycondensation of a polyol,polyacid and fatty acid are used in the coating industry in a variety ofproducts, including chemical resins, enamels, varnishes and paints.These polyesters also are used in the food industry to make texturizedoils and emulsions for use as fat substitutes.

While much progress has been made in the field of polymericbiomaterials, further developments must be made in order for suchbiomaterials to be used optimally in the body. There is a great need forpolymers for use in drug delivery, tissue engineering and medicaldevices, where the polymers have functional pendant groups that wouldallow, e.g., attachment of drugs, improvement of biocompatibility orpromotion of bioadhesion. Polyesters containing functional comonomersare known. However, the chemistry involved in the synthesis offunctional monomers is often very complex and results in poor yields.

SUMMARY OF THE INVENTION

The present invention is directed to a synthetic, biodegrable,biocompatible polymer comprising the reaction product of anα,β-unsaturated polybasic acid or derivative thereof, a monoglyceride,and further comprising a functional agent pended thereto to provide thepolymer with certain desired properties. The invention also is directedto compositions for medical applications and medical devices containingsuch polymers.

DETAILED DESCRIPTION OF THE INVENTION

Alkyd polymers have been prepared by several known methods. For example,alkyd-type polymers were prepared by Van Bemmelen (J. Prakt. Chem., 69(1856) 84) by condensing succinic anhydride with glycerol. In the “FattyAcid” method (see Parkyn, et al. Polyesters (1967), Iliffe Books,London, Vol. 2 and Patton, In: Alkyd Resins Technology,Wiley-Interscience New York (1962)), a fatty acid, a polyol and ananhydride are mixed together and allowed to react. The “FattyAcid-Monoglyceride” method includes a first step of esterifying thefatty acid with glycerol and, when the first reaction is complete,adding an acid anhydride. The reaction mixture then is heated and thepolymerization reaction takes place. In the “Oil-Monoglyceride” method,an oil is reacted with glycerol to form a mixture of mono-, di-, andtriglycerides. This mixture then is polymerized by reacting with an acidanhydride.

The synthetic, biodegradable, biocompatible polymers utilized in thepresent invention are the reaction product of an α,β-unsaturatedpolybasic acid or derivative thereof, a monoglyceride, and a functionalagent. Preferably, the polymers of the present invention are prepared bythe polycondensation first of an α,β-unsaturated polybasic acid orderivative thereof with a monoglyceride to form an alkyd polyesterpolymer. The monoglyceride comprises reactive hydroxy groups and fattyacid groups.

The alkyd polyester polymer is reacted with the functional agent to formthe functionalized alkyd polyester of the present invention. Thefunctional agent comprises a first functional moiety that is a strongnucleophile, such as a thiol or amine, that can react with theα,β-unsaturated acid through a Michael addition reaction, thus pendingthe functional agent to the polymer. A “strong nucleophile” is amolecule that is capable of donating an electron pair to an electrophilein a polar-bond forming reaction. Preferably, the strong nucleophile ismore nucleophilic than H₂O at physiologic pH.

The functional agent also comprises a second functional moiety, such asa hydroxyl, carboxyl, amine and the like, in order to provide thepolymer with certain desired properties. For example; the functionalagent may be selected to provide desired solubility properties or toadjust pH, depending upon the particular application. The functionalagent may be selected based upon the ability of the second moiety'sability to react with certain therapeutic agents, e.g. pharmaceuticaldrugs. The second moiety also may provide desiredhydrophobicity/hydrophilicity to the polymer. In addition, theadhesiveness of the polymer may be adjusted depending upon selection ofthe functional moiety.

The polymers comprise an aliphatic polyester backbone with pendant fattyacid ester groups on the monoglyceride unit and the second functionalmoiety, e.g. hydroxyl, carboxyl or amine, pendant from the diacid unit.Long chain saturated fatty acids result in polymers that are solids thatexhibit relatively low melting points, e.g. between about 25° C. and 70°C. Alternatively, use of unsaturated fatty acids or short chain fattyacids results in liquid polymers. As used herein, a liquid polymer is apolymer with a melt temperature of less than about 25° C., preferablyless than about 20° C.

The solid polymers and/or liquid polymers can be used to form injectablemicrodispersions. The microdispersions can be formed by physicallyblending either liquid polymers or finely ground solid polymers of thepresent invention with compatible polymers. In one embodiment, themicrodispersions can be formed by physically blending liquid polymers ofthe present invention with finely ground solid polymers of the presentinvention. Upon blending, the solid polymer particle phase is dispersedthrough the polymeric liquid phase.

Generally, the solid polymers will have an average particle diameter ofless than about 500 microns and preferably less than 50 microns. It iscurrently preferred to mix the finely ground solid polymer and theliquid polymer and raise the temperature of the mixture to a temperaturesufficient to melt the solid polymer (melt blending), thereby providinga dispersion of a first polymeric liquid phase dispersed in a secondpolymeric liquid phase . Upon cooling, the first dispersed liquidpolymeric phase participates to form a solid polymer phase dispersed inthe second polymeric liquid phase. Melt blending is preferred because itsimplifies the mixing operation involved in producing themicrodispersion. It is desirable to avoid excessive heating during meltblending to avoid transesterification of the polymers.

Monoglycerides that may be used to prepare the polymers utilized in thepresent invention include, without limitation, monostearoyl glycerol,monopalmitoyl glycerol, monomyrisitoyl glycerol, monocaproyl glycerol,monodecanoyl glycerol, monolauroyl glycerol, monolinoleoyl glycerol,monooleoyl glycerol, and combinations thereof. Preferred monoglyceridesinclude monostearoyl glycerol, monopalmitoyl glycerol and monomyrisitoylglycerol.

α,β-unsaturated polybasic acids that can be used include multifunctionalcarboxylic acids, such as maleic, fumaric, citraconic itaconic- acid andthe like. Polybasic acid derivatives include anhydrides, such as maleicanhydride, mixed anhydrides, esters, activated esters and acid halides.The multifunctional carboxylic acids listed above are preferred.

In another embodiment, other polybasic acids such as succinic, glutaric,adipic, pimelic, suberic and sebacic acids could also be used to makecopolymers with the α,β-unsaturated acids listed above.

The functionalized alkyd polyesters of the present invention are madeusing the well known Michael addition reaction. The functional agentcomprises a first functional moiety comprising a strong nucleophile,such as a thiol or amine, in order to provide reaction with and bindingto the alkyd polyester. The functional agent also comprises a secondfunctional moiety such as an alcohol, amine, acid, sulfate, solfonateand the like, in order to provide the functionalized alkyd polyesterwith certain properties. The choice of the functional agent will dependon the particular polymer to be generated and also upon the propertiesrequired for the particular anticipated or desired use of thefunctionalized polymer. One skilled in the art of medical devices andcompositions, once having the benefit of this disclosure, will be ableto readily ascertain the particular functional agent required for theparticular properties desired under the particular circumstance.Suitable functional agents include, without limitation, mercaptoethanol,mercaptopropanol, mercaptobutanol, mercaptohexanol, mercaptopropanediol,mercaptoacetic acid, mercaptopropionic acid, mercaptosuccinic acid andmercaptoethylamine.

In certain embodiments of the invention, the alkyd polyester may beprepared from the polybasic acid or derivative thereof, themonoglyceride and, additionally, at least one additional polyol selectedfrom the group consisting of ethylene glycol, 1,2-propylene glycol,1,3-propanediol, bis-2-hydroxyethyl ether, 1,4-butanediol,1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol,1,12-dodecanediol, other diols, linear poly(ethylene glycol), branchedpoly(ethylene glycol), linear poly(propylene glycol), branchedpoly(propylene glycol), linear poly(ethylene-co-propylene glycol)s andbranched poly(ethylene-co-propylene glycol)s. In preparing the polymersof the present invention, the particular chemical and mechanicalproperties required of the polymer for a particular use must beconsidered. For example, changing the chemical composition can vary thephysical and mechanical properties, including absorption times.Copolymers can be prepared by using mixtures of diacids, differentmonoalkanoyl glycerides and different functional moieties to match adesired set of properties. Similarly, blends of two or morefunctionalized alkyds may be prepared to tailor properties for differentapplications.

A variety of biological active substances, hereinafter referred to asbioactive agents, can be covalently attached to the functionalizedpolymers by known coupling chemistry to provide sustained release of thebioactive agent. As used herein, bioactive agent is meant to includethose substances or materials that have a therapeutic effect on mammals,e.g. pharmaceutical compounds.

The polymerization of the alkyd polyesters preferably is performed undermelt polycondensation conditions in the presence of an organometalliccatalyst at elevated temperatures. The organometallic catalystpreferably is a tin-based catalyst, e.g. stannous octoate. The catalystpreferably will be present in the mixture at a mole ratio of polyol andpolycarboxylic acid to catalyst in the range of from about 15,000/1 to80,000/1. The reaction preferably is performed at a temperature no lessthan about 120° C. Higher polymerization temperatures may lead tofurther increases in the molecular weight of the copolymer, which may bedesirable for numerous applications. The exact reaction conditionschosen will depend on numerous factors, including the properties of thepolymer desired, the viscosity of the reaction mixture, and meltingtemperature of the polymer. The preferred reaction conditions oftemperature, time and pressure can be readily determined by assessingthese and other factors.

Generally, the reaction mixture will be maintained at about 180° C. Thepolymerization reaction can be allowed to proceed at this temperatureuntil the desired molecular weight and percent conversion is achievedfor the copolymer, which typically will take from about 15 minutes to 24hours. Increasing the reaction temperature generally decreases thereaction time needed to achieve a particular molecular weight.

In another embodiment, copolymers of alkyd polyesters can be prepared byforming an alkyd polyester prepolymer polymerized under meltpolycondensation conditions, then adding at least one lactone monomer orlactone prepolymer. The mixture then would be subjected to the desiredconditions of temperature and time to copolymerize the prepolymer withthe lactone monomers.

The molecular weight of the prepolymer, as well as its composition, canbe varied depending on the desired characteristic that the prepolymer isto impart to the copolymer. Those skilled in the art will recognize thatthe alkyd polyester prepolymers described herein can also be made frommixtures of more than one monoglyceride and dicarboxylic acid.

The addition of the functional agent comprising the nucleophilic reagentto the alkyd polyester having an α,β-unsaturated group can be carriedout at room temperature or at 60° C. for 24 hours using benzoylperoxide/dimethylaminopyridine or azobis isobutyronitrile (AIBN) ascatalyst. Alternatively, the reaction may be performed at roomtemperature for 14 hours using triethylamine as catalyst.

The polymers, copolymers and blends of the present invention can becrosslinked to affect mechanical properties. Crosslinking can beaccomplished by the addition of crosslinking enhancers, irradiation,e.g. gamma-irradiation, or a combination of both. In particular,crosslinking can be used to control the amount of swelling that thematerials of this invention experience in water.

One of the beneficial properties of the functionalized alkyd polyestersof this invention is that the ester linkages in the alkyd block arehydrolytically unstable and, therefore, the polymer is biodegradablebecause it readily breaks down into small segments when exposed to moistbody tissue. The segments then either are absorbed by the body, orpassed by the body. More particularly, the biodegraded segments do notelicit permanent chronic foreign body reaction, because they areabsorbed by the body, such that no permanent trace or residual of thesegment is retained by the body. In this regard, while it is envisionedthat co-reactants could be incorporated into the reaction mixture of thepolybasic acid and the diol for the formation of the functionalizedalkyds, it is preferable that the reaction mixture does not contain aconcentration of any co-reactant that would render the subsequentlyprepared polymer nonbiodegradable or nonabsorbable. Preferably, thereaction mixture is substantially free of any such co-reactants if theresulting polymer is rendered nonbiodegradable or nonabsorbable.

The functionalized polymers of the present invention may be used invarious medical devices for various purposes. One skilled in the art,once having the benefit of this disclosure, will be able to readilyutilize the polymers in various medical devices. Examples of suchmedical devices include suture anchor devices, sutures, staples,surgical tacks, clips, plates, screws, drug-delivery devices, adhesionprevention films and foams, and tissue adhesives.

In one embodiment of the invention, the functionalized alkyd polyestersof the present invention can be used as a pharmaceutical carrier in adrug delivery matrix. Solid functionalized alkyd polyesters could beused to coat or encapsulate a bioactive agent. Alternatively, aneffective amount of a bioactive agent could be mixed with injectablemicrodispersions of solid and liquid polymers. Such a microdispersionwould be particularly suitable for unstable drugs such as proteins.

The variety of bioactive agents that can be used in conjunction with thepolymers of the invention is vast. In general, bioactive agents whichmay be administered via pharmaceutical compositions of the inventioninclude, without limitation, antiinfectives, such as antibiotics andantiviral agents; analgesics and analgesic combinations; anorexics;antihelmintics; antiarthritics; antiasthmatic agents; anticonvulsants;antidepressants; antidiuretic agents; antidiarrheals; antihistamines;antiinflammatory agents; antimigraine preparations; antinauseants;antineoplastics; antiparkinsonism drugs; antipruritics; antipsychotics;antipyretics; antispasmodics; anticholinergics; sympathomimetics;xanthine derivatives; cardiovascular preparations including calciumchannel blockers and beta-blockers such as pindolol and antiarrhythmics;antihypertensives; diuretics; vasodilators, including general coronary,peripheral and cerebral; central nervous system stimulants; cough andcold preparations, including decongestants; hormones, such as estradioland other steroids, including corticosteroids; hypnotics;immunosuppressives; muscle relaxants; parasympatholytics;psychostimulants; sedatives; tranquilizers; naturally derived orgenetically engineered proteins, growth factors, polysaccharides,glycoproteins or lipoproteins; oligonucleotides; antibodies; antigens;cholinergics; chemotherapeutics; hemostatics; clot dissolving agents;radioactive agents; and cystostatics.

Rapamycin, risperidone, and erythropoietin are preferred bioactiveagents that may be used in drug delivery matrices of the presentinvention.

The drug delivery matrix may be administered in any suitable dosage formsuch as oral, parenteral, pulmonary, buccal, nasal, ocular, topical,vaginal routes, or as a suppository. Bioerodible particles, ointments,gels, creams, and similar soft dosage forms adapted for theadministration via the above routes may also be formulated. Other modesof administration, e.g. transdermal, and compositional forms, e.g. morerigid transdermal forms, are within the scope of the invention as well.

Parenteral administration of a bioerodible composition of the inventioncan be effected by either subcutaneous or intramuscular injection. Thebioactive agent could be encapsulated in particles made of the solidpolymer. Alternatively, parenteral formulations of the copolymer may beformulated by mixing one or more pharmaceuticals with a liquid copolymeror microdispersion. Other suitable parenteral additives may beformulated with the copolymer and pharmaceutical active. However, ifwater is to be used it should be added immediately beforeadministration. Bioerodible ointment, gel or cream may also be injectedas is or in combination with one or more suitable auxiliary componentsas described below. Parenteral delivery is preferred for administrationof proteinaceous drugs such as growth factors, growth hormone, or thelike.

The bioerodible ointments, gels and creams of the invention will includean ointment, gel or cream base comprising one or more of the copolymersdescribed herein and a selected bioactive agent. The bioactive agent,whether present as a liquid, a finely divided solid, or any otherphysical form, is dispersed in the ointment, gel or cream base.Typically, but optionally, the compositions include one or more othercomponents, e.g., nontoxic auxiliary substances such as colorants,diluents, odorants, carriers, excipients, stabilizers or the like.

The quantity and type of copolymers incorporated into the parenteral,ointment, gel, cream, etc., is variable. For a more viscous composition,a higher molecular weight polymer is used. If a less viscous compositionis desired, a lower molecular weight polymer can be employed. Theproduct may contain blends of the liquid or low melting point copolymersto provide the desired release profile or consistency to a givenformulation.

While not essential for topical or transdermal administration of manydrugs, in some cases, it may be preferred that a skin permeationenhancer be co-administered with the drug. Any number of the many skinpermeation enhancers known in the art may be used. Examples of suitableenhancers include dimethylsulfoxide (DMSO), dimethylformamide (DMF),N,N-dimethylacetamide (DMA), deslymethylsulfoxide, ethanol, eucalyptol,lecithin, and the 1-N-dodecylcyclazacycloheptan-2-ones.

Depending on dosage form, the pharmaceutical compositions of the presentinvention may be administered in different ways, i.e. parenterally,topically, or the like. Preferred dosage forms are liquid dosage formsthat can be administered parenterally.

The amount of bioactive agent will be dependent upon the particular drugemployed and medical condition being treated. Typically, the amount ofdrug represents about 0.001% to about 70%, more typically about 0.001%to about 50%, most typically about 0.001% to about 20% by weight of thematrix.

The quantity and type of alkyd incorporated into the parenteral willvary depending on the release profile desired and the amount of drugemployed. The product may contain blends of polymers to provide thedesired release profile or consistency to a given formulation.

The functionalized alkyd polyester, upon contact with body fluids,including blood or the like, undergoes gradual degradation, mainlythrough hydrolysis, with concomitant release of the dispersed drug for asustained or extended period, as compared to the release from anisotonic saline solution. This can result in prolonged delivery ofeffective amounts of drug, e.g. over about 1 to about 2,000 hours,preferably about 2 to about 800 hours, or, e.g. 0.0001 mg/kg/hour to 10mg/kg/hour. This dosage form can be administered as is necessary,depending on the subject being treated, the severity of the affliction,the judgment of the prescribing physician, and the like.

Individual formulations of drugs and polyether alkyd may be tested inappropriate in vitro and in vivo models to achieve the desired drugrelease profiles. For example, a drug could be formulated with afunctionalized alkyd polyester and orally administered to an animal. Thedrug release profile could then be monitored by appropriate means, suchas by taking blood samples at specific times and assaying the samplesfor drug concentration. Following this or similar procedures, thoseskilled in the art will be able to formulate a variety of formulations.

In a further embodiment of the present invention, the polymers andblends thereof can be used in tissue engineering applications, e.g. assupports for cells or delivery vehicle for cells. Appropriate tissuescaffolding structures are known in the art, such as the prostheticarticular cartilage described in U.S. Pat. No. 5,306,311, the porousbiodegradable scaffolding described in WO 94/25079, and theprevascularized implants described in WO 93/08850 (all herebyincorporated by reference herein). Methods of seeding and/or culturingcells in tissue scaffoldings are also known in the art such as thosemethods disclosed in EPO 422 209 B1, WO 88/03785, WO 90/12604 and WO95/33821, all of which are all hereby incorporated by reference hereinas if set forth in their entirety.

In another embodiment, the functionalized alkyd polyester is used tocoat a surface of a medical device to enhance the lubricity of thecoated surface. The polymer may be applied as a coating usingconventional techniques. For example, the polymer may be solubilized ina dilute solution of a volatile organic solvent, such as acetone,methanol, ethyl acetate or toluene, and then the article can be immersedin the solution to coat its surface. Once the surface is coated, thesurgical article can be removed from the solution where it can be driedat an elevated temperature until the solvent and any residual reactantsare removed.

Although it is contemplated that numerous surgical articles, includingbut not limited to endoscopic instruments, can be coated with thepolymers of this invention to improve the surface properties of thearticle, the preferred surgical articles are surgical sutures andneedles. The most preferred surgical article is a suture, mostpreferably attached to a needle. Preferably, the suture is a syntheticabsorbable suture. These sutures are derived, for example, fromhomopolymers and copolymers of lactone monomers such as glycolide,lactide, including L-lactide D-lactide, meso-lactide and rac-lactide,ε-caprolactone, p-dioxanone, 1,4-dioxanone, 1,4-dioxepan-2-one,1,5-dioxepan-2-one and trimethylene carbonate. The preferred suture is abraided multifilament suture composed of polyglycolide orpoly(glycolide-co-lactide).

The amount of coating polymer to be applied on the surface of a braidedsuture can be readily determined empirically and will depend on theparticular copolymer and suture chosen. Ideally, the amount of coatingcopolymer applied to the surface of the suture may range from about 0.5to about 30 percent of the weight of the coated suture, more preferablyfrom about 1.0 to about 20 weight percent, most preferably from 1 toabout 5 weight percent. If the amount of coating on the suture weregreater than about 30 weight percent, then it may increase the risk thatthe coating may flake off when the suture is passed through tissue.

Sutures coated with the polymers of this invention are desirable becausethey have a more slippery feel, thus making it easier for the surgeon toslide a knot down the suture to the site of surgical trauma. Inaddition, the suture is more pliable and, therefore, is easier for thesurgeon to manipulate during use. These advantages are exhibited incomparison to sutures which do not have their surfaces coated with thepolymer of this invention.

In another embodiment of the present invention, when the article is asurgical needle, the amount of coating applied to the surface of thearticle is an amount which creates a layer with a thickness rangingpreferably between about 2 to about 20 microns on the needle, morepreferably about 4 to about 8 microns. If the amount of coating on theneedle were such that the thickness of the coating layer was greaterthan about 20 microns, or if the thickness was less than about 2microns, then the desired performance of the needle as it is passedthrough tissue may not be achieved.

In another embodiment of the present invention, functionalized alkydpolyesters of the present invention can be used to overcoatmicroparticles encapsulating a bioactive agent(s). This would helpprovide an additional barrier for sustained release of the drug.

In yet another embodiment, the functionalized alkyd polyesters of thepresent invention could be used to form a bone replacement materialcomprising the solid polymer, or the liquid polymer, or amicrodispersion of the polymers of the current invention and inorganicfiller. The inorganic filler may be selected from alpha-tricalciumphosphate, beta-tricalcium phosphate, calcium carbonate, bariumcarbonate, calcium sulfate, barium sulfate, hydroxyapatite, and mixturesthereof. In certain embodiments the inorganic filler comprises apolymorph of calcium phosphate. Preferably, the inorganic filler ishydroxyapatite. The bone replacement materials may further comprise abioactive agent in a therapeutically effective amount, such a growthfactor, to facilitate growth of bone tissue. Furthermore, the bonereplacement material may comprise a biologically derived substanceselected from the group consisting of demineralized bone, platelet richplasma, bone marrow aspirate and bone fragments. The relative amounts ofpolymeric wax and inorganic filler may be determined readily by oneskilled in the art by routine experimentation after having the benefitof this disclosure.

The injectable microdispersions can be used for a variety of soft tissuerepair and augmentation procedures. For example, the microdispersionscan be used in facial tissue repair or augmentation, including but notlimited to camouflaging scars, filling depressions, smoothing outirregularity, correcting asymmetry in facial hemiatrophy, secondbranchial arch syndrome, facial lipodystrophy and camouflagingage-related wrinkles as well as augmenting facial eminences, e.g. lips,brow, etc. Additionally, these injectable microdispersions can be usedto restore or improve sphincter function, such as for treating stressurinary incontinence. Other uses of these injectable microdispersionsmay also include the treatment of vesicoureteral reflux (incompletefunction of the inlet of the ureter in children) by suburetericinjection and the application of these microdispersions as generalpurpose fillers in the human body.

Surgical applications for an injectable, biodegradable microdispersioninclude, but are not limited to, facial contouring, e.g. frown orglabellar line, acne scars, cheek depressions, vertical or perioral liplines, marionette lines or oral commissures, worry or forehead lines,crow's feet or periorbital lines, deep smile lines or nasolabial folds,smile lines, facial scars, lips and the like; periurethral injection,including injection into the submucosa of the urethra along the urethra,at or around the urethral-bladder junction to the external sphincter;urethral injection for the prevention of urinary reflux; injection intothe tissues of the gastrointestinal tract for the bulking of tissue toprevent reflux; to aid in sphincter muscle coaptation, internal orexternal, and for coaptation of an enlarged lumen; intraocular injectionfor the replacement of vitreous fluid or maintenance of intraocularpressure for retinal detachment; injection into anatomical ducts totemporarily plug the outlet to prevent reflux or infection propagation;larynx rehabilitation after surgery or atrophy; and any other softtissue which can be augmented for cosmetic or therapeutic effect.Surgical specialists who would use such a product include, but are notlimited to, plastic and reconstructive surgeons; dermatologists; facialplastic surgeons, cosmetic surgeons, otolaryngologists; urologists;gynecologists; gastroenterologists; ophthalmologists; and any otherphysician qualified to utilize such a product.

Additionally, to facilitate the administration and treatment of patientswith the inventive microdispersion, pharmaceutically active compounds oradjuvants can be administered therewith. Pharmaceutically active agentsthat may be co-administered with the inventive microdispersion include,but are not limited to, anesthetics, e.g. lidocaine; andantiinflammatories, e.g. cortisone.

The microdispersion can be administered with a syringe and needle or avariety of devices. It is also envisioned that the microdispersion couldbe sold in the form of a kit comprising a device containing themicrodispersion. The device having an outlet for said microdispersion,an ejector for expelling the microdispersion and a hollow tubular memberfitted to the outlet for administering the microdispersion into ananimal.

The dosage forms for the microdispersions of the invention aresustained-release parenterals, bioerodible ointments, gels, creams, andsimilar soft dosage forms.

The examples set forth below are for illustration purposes only and arenot intended to limit the scope of the claimed invention in any way.Numerous additional embodiments within the scope and spirit of theinvention will become readily apparent to those skilled in the art.

In the examples below, the synthesized polymers were characterized viadifferential scanning calorimetry (DSC), gel permeation chromatography(GPC), and nuclear magnetic resonance (NMR) spectroscopy. DSCmeasurements were performed on a 2920 Modulated Differential ScanningCalorimeter from TA Instruments using aluminum sample pans and sampleweights of 5-10 milligrams. Samples were heated from room temperature to100° C. at 10° C./minute; quenched to −40° C. at 30° C./minute followedby heating to 100° C. at 10° C./minute. For GPC, a Waters System withMillennium 32 Software and a 410 Refractive Index Detector were used.Molecular weights were determined relative to polystyrene standardsusing THF as the solvent. Proton NMR was obtained in deuteratedchloroform on a 400 MHz NMR spectrometer using Varian software.

EXAMPLE 1 Synthesis of a Copolymer of Monooleoyl Glyceride and MaleicAnhydride

142.6 grams of monoleoyl glycerol were added to a dry 250 ml, singleneck, round bottom flask. A stir bar, was added and a nitrogen inletadapter was attached. The reaction flask was placed in a roomtemperature oil bath and a nitrogen gas blanket was started. The flaskwas heated to 140° C., and 39.2 grams of maleic anhydride were added.The temperature was raised to 190° C. and maintained for 3 hours. After3 hours the flask was removed from the oil bath to cool to roomtemperature. The polymer was a pale yellow, viscous liquid. GPCmeasurement determined a number average molecular weight of 1383, and aweight average molecular weight of 6435.

EXAMPLE 2 Synthesis of Copolymer of Monooleoyl Glyceride and MaleicAnhydride and 5 mol % PEG400

40.1 grams of monooleoyl glycerol and 5.0 grams of PEG400 were added toa dry 100 ml, single neck, round bottom flask. A stir bar was added anda nitrogen inlet adapter was attached. The reaction flask was placedinto a room temperature oil bath and a nitrogen blanket was applied. Theoil bath temperature was raised to 140° C. Once at 140° C., 12.3 gramsof maleic anhydride were added. The temperature was raised to 180° C.and maintained for 7 hours at 180° C. The flask was removed from the oilbath and allowed to cool to room temperature. The polymer was a paleyellow, viscous liquid.

GPC measurement determined a number average molecular weight of 1122,and a weight average molecular weight of 5647.

EXAMPLE 3 Synthesis of Copolymer of Monooleoyl Glyceride and MaleicAnhydride and 25 mol % PEG400

17.8 grams of monooleoyl glycerol and 20.0 grams of PEG400 were added toa dry 100 ml, single neck, round bottom flask. A stir bar was added anda nitrogen inlet adapter was attached. The reaction flask was placedinto a room temperature oil bath and a nitrogen blanket was applied. Theoil bath temperature was raised to 140° C. Once at 140° C., 9.8 grams ofmaleic anhydride were added. The temperature was raised to 180° C. andmaintained for 7 hours at 180° C. The flask was removed from the oilbath and allowed to cool to room temperature. The polymer was a paleyellow, viscous liquid.

GPC measurement determined a number average molecular weight of 1230,and a weight average molecular weight of 4481.

EXAMPLE 4 Reaction of Mercaptoethanol with Copolymer of MonooleoylGlyceride and Maleic Anhydride

5.0 grams of a copolymer of monooleoyl glyceride and maleic anhydridemade following the procedure of Example 1, 0.77 ml of mercaptoethanoland 11 ml of DMF were added to a dry 50 ml, single neck, round bottomflask along with 52 milligrams of azobis isobutyronitrile (AIBN). A stirbar was added and a nitrogen inlet adapter was attached. The reactionflask was placed in a room temperature oil bath and a nitrogen blanketwas started. The temperature was raised to 60° C. and maintained for 24hours. After 24 hours, the flask was removed from the oil bath to coolto room temperature. The polymer was diluted with 10 mL of ethyl acetateand then washed twice with an aqueous NaCl solution, dried with MgSO₄,and filtered through a filter paper. The solvent was removed by rotaryevaporation followed by vacuum drying. The polymer was a yellow,transparent viscous liquid.

¹H NMR showed that there was no α,β-unsaturated ester remaining in thepolymer (no peak at 6.8 ppm). ¹H NMR (400 MHz, CD₃Cl, ppm): δ 0.86triplet (3H), 1.26 multiplet (22H), 1.61 multiplet (2H), 2.00 multiplet(4H), 2.30 multiplet (2H), 2.80 multiplet (3H), 3.00 doublet (2H), 3.80multiplet (2H), 4.20 multiplet (5H), 5.38 multiplet (2H), 8.00 singlet(1H). IR confirms the presence of hydroxy functional groups. IR (ZnS):3442, 2920, 2860, 1745, 1456, 1168 cm⁻¹.

EXAMPLE 5 Reaction of Mercaptopropionic Acid with Copolymer ofMonooleoyl Glyceride and Maleic Anhydride

5.0 grams of copolymer of monooleoyl glyceride and maleic anhydride madefollowing the procedure of Example 1, 0.98 ml of mercaptopropionic acid,and 11 ml of DMF were added to a dry 50 ml, single neck, round bottomflask along with 54 mg (or 3 mole percent) of AIBN. A stir bar was addedand a nitrogen inlet adapter was attached. The reaction flask was placedin a room temperature oil bath and a nitrogen blanket was started. Thetemperature was raised to 60° C. and maintained for 24 hours. After 24hours, the flask was removed from the oil bath to cool to roomtemperature. The polymer was diluted with 10 ml of ethyl acetate, washedwith 0.01M NaOH, and then washed twice with an aqueous NaCl solution,dried with MgSO₄, and filtered through a filter paper. The solvent wasremoved by rotary evaporation followed by vacuum drying. The polymer wasa yellow, transparent viscous liquid.

¹H NMR showed that there was no α,β-unsaturated ester remaining in thepolymer (no peak at 6.8 ppm). ¹H NMR (400 MHz, CD₃Cl, ppm): δ 0.86triplet (3H), 1.26 multiplet (22H), 1.45 multiplet (3H), 1.61 multiplet(2H), 2.00 multiplet (4H), 2.30 multiplet (2H), 2.90 multiplet (3H),3.00 doublet (2H), 3.70 multiplet (2H), 4.20 multiplet (5H), 5.38multiplet (2H), 8.00 singlet (1H). IR confirms the presence of hydroxyfunctional groups. IR (ZnS): 3437, 3213, 2920, 2860, 1745, 1456, 1168cm⁻¹.

EXAMPLE 6 Reaction of Mercaptoethylamine with Copolymer of MonooleoylGlyceride and Maleic Anhydride

5.0 grams of copolymer of monooleoyl glyceride and maleic anhydride madefollowing the procedure of Example 1, 0.85 ml of mercaptoethylamine and11 ml of DMF were added to a dry 50 ml, single neck, round bottom flaskalong with 54 mg of AIBN. A stir bar was added and a nitrogen inletadapter was attached. The reaction flask was placed in a roomtemperature oil bath and a nitrogen blanket was started. The temperaturewas raised to 60° C. and maintained for 24 hours. After 24 hours, theflask was removed from the oil bath to cool to room temperature. Thepolymer was diluted with 10 ml of ethyl acetate, washed with 0.01M NaOH,and then washed twice with an aqueous NaCl solution, dried with MgSO₄,and filtered through a filter paper. The solvent was removed by rotaryevaporation followed by vacuum drying. The polymer was a yellow,transparent viscous liquid.

¹H NMR showed that there was no α,β-unsaturated ester remaining in thepolymer (no peak at 6.8 ppm). ¹H NMR (400 MHz, CD₃Cl, ppm): δ 0.86triplet (3H), 1.26 multiplet (22H), 1.61 multiplet (2H), 2.00 multiplet(4H), 2.30 multiplet (2H), 2.80 multiplet (2H), 3.60 multiplet (2H),4.20 multiplet (3H), 5.38 multiplet (2H). IR confirms the presence ofamine functional groups. IR (ZnS): 3346, 2920, 2860, 1745, 1660, 1456,1168 cm⁻¹.

EXAMPLE 7 Reaction of O-(2-aminoethyl)-O′-methylpolyethyleneglycol 5000with Copolymer of Monooleoyl Glycerol and Maleic Anhydride

1.0 gram of poly(glyceryl monooleate-succinate), 11.1 g ofO-(2-aminoethyl)-O′-methylpolyethyleneglycol 5000, and 11 ml of DMF wereadded to a dry 50 ml, single neck, round bottom flask along with 10.8milligrams of AIBN. A stir bar was added and a nitrogen inlet adapterwas attached. The reaction flask was placed in a room temperature oilbath and a nitrogen blanket was started. The temperature was raised to60° C. and maintained for 24 hours. After 24 hours, the flask wasremoved from the oil bath to cool to room temperature. The polymer wasdiluted with 10 ml of ethyl acetate and then washed twice with anaqueous NaCl solution, dried with MgSO₄, and filtered through a filterpaper. The solvent was removed by rotary evaporation followed by vacuumdrying. The polymer was a white solid.

¹H NMR showed that there was no α,β-unsaturated ester remaining in thepolymer (no peak at 6.8 ppm). ¹H NMR (400 MHz, CD₃Cl, ppm): δ 0.86triplet (3H), 1.26 multiplet (22H), 1.61 multiplet (2H), 2.00 multiplet(4H), 2.20 multiplet (22H), 3.60 multiplet (400H), 5.38 multiplet (2H).IR (ZnS): 3473, 2860, 1745, 1456, 1342, 1282, 1242, 1113, 968, 844 cm⁻¹.

1. A synthetic polymer comprising the reaction product of an α,β-unsaturated polybasic acid or derivative thereof; and a monoglyceride;said polymer comprising an aliphatic polyester backbone with pendantfatty acid ester groups on the monoglyceride unit and further comprisingpended thereto a functional agent comprising a first functionalnucleophilic moiety and a second functional moiety other than said firstfunctional moiety, said second functional moiety pended to saidα,β-unsaturated polybasic acid or derivative thereof.
 2. The polymer ofclaim 1 wherein said α,β-unsaturated polybasic acid or derivativethereof is selected from the group consisting of maleic acid, fumaricacic, citraconic acid, itaconic acid, maleic anhydride, mixedanhydrides, esters, activated esters and acid halides.
 3. The polymer ofclaim 1 wherein said monoglyceride is selected from the group consistingof monostearoyl glycerol, monopalmitoyl glycerol, monomyrisitoylglycerol, monocaproyl glycerol, monodecanoyl glycerol, monolauroylglycerol, monolinoleoyl glycerol and monooleoyl glycerol.
 4. The polymerof claim 3 wherein said α,β-unsaturated polybasic acid derivative ismaleic anhydride.
 5. The polymer of claim 3 wherein said α,β-unsaturatedpolybasic acid is maleic acid.
 6. The polymer of claim 1 wherein saidfunctional agent is selected from the group consisting ofmercaptoethanol, mercaptopropanol, mercaptobutanol, mercaptohexanol,mercaptopropanediol, mercaptoacetic acid, mercaptopropionic acid,mercaptosuccinic acid and mercaptoethylamine.
 7. The polymer of claim 1wherein said polymer is branched.
 8. The polymer of claim 1 wherein saidpolymer comprises the reaction product of said monoglyceride, and atleast two of said α,β-unsaturated polybasic acids or derivatives thereofselected from the group consisting of maleic acid, fumaric acic,citraconic acid, itaconic acid, maleic anhydride, mixed anhydrides,esters, activated esters and acid halides.
 9. The polymer of claim 1wherein said polymer comprises the reaction product of saidmonoglyceride, said α,β-unsaturated polybasic acids or derivativesthereof, and a polybasic acid selected from the group consisting ofsuccinic acid, glutaric acid, adipic acid, pimelic acid, suberic acidand sebacic acid.
 10. The polymer of claim 1 wherein said polymercomprises the reaction product of said α,β-unsaturated polybasic acid orderivative thereof, and at least two monoglycerides selected from thegroup consisting of monostearoyl glycerol, monopalmitoyl glycerol,monomyrisitoyl glycerol, monocaproyl glycerol, monodecanoyl glycerol,monolauroyl glycerol, monolinoleoyl glycerol and monooleoyl glycerol.